Powhatan Wildlife Management Area
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Powhatan Wildlife Management Area clear sky chart from 2005-11-06 to 2024-11-04.

This page is a summary of past forecasts. Even though it's based only on forecasts, some people use these pages as clue to a site's climate. But climate data based on actual observation should be preferred (if you can find it!).

Cloud, Transparency and Seeing forecasts are summarized individually. But because good observing conditions require a combination of minimum cloud cover, transparency and seeing, the individual forecast summaries can be difficult to interpret. The observing conditions section counts the combinations of conditions needed for common types of astronomical observation.

Observing Conditions

The following tables count the occurrence of the combinations of forecast and darkness conditions needed for different observations. Conditions are rated by by what percentage of the hours the observation would likely be attempted are usable.

Observation Type	Minimum conditions for hour to be usable				Out of hours
	Clear of Clouds	Transparency	Seeing	Sky Brightness
Planetary:	50%	(no limit)	Average	(no limit)	Nighttime Hours
Deep Sky:	70%	Average	(no limit)	5.9	Nighttime Hours
CCD Imaging:	70%	Below Average	Poor	(no limit)	Nighttime Hours

Percentages are of nighttime hours per month, or per year, when a particular observing conditions was met. Deep Sky percentages never exceed 50% because the moon is up half the time. Deep sky percentages are much lower for charts at high latitudes because of fewer dark hours in the summer.

Overall

By Month

Individual Forecasts

The length of each colored bar in the "occurrence of each Forecast" column is proportional to the number of times the chart forecast that color. The percentages are of the total number of hours per month, or per year, with a particular forecast. The colors as the same as those used in clear sky charts.

Note: Transparency probabilities are only counted for those hours that have 30% or less cloud cover. Seeing probabilities are only counted for those hours that have 80% or less cloud cover. If that's too tricky, try Observing Conditions instead.

Overall

		Occurrence of each Forecast	Data Points
Cloud Cover	Day	14% 6% 2 6% 4 4 4 4 6% 8% 42%	100978
	Night	14% 6% 2 6% 4 4 4 4 5% 7% 43%	97978
Transparency	Day	37% 7% 12% 22% 17% 4	104627
	Night	38% 6% 11% 22% 18% 5%	102468
Seeing	Day	19% 11% 26% 24% 15% 5%	15112
	Night	17% 10% 27% 31% 14% 1	24830

By Month

Percentage Cloud Cover SE (2006-)
Color Meanings: Overcast 90% covered 80% covered 70% covered 60% covered 50% covered 40% covered 30% covered 20% covered 10% covered Clear
Month	Days in Month		Occurrence of each Forecast	Data Points
January	1st to 10th	Day	18% 5% 2 4 3 3 4 3 4 5% 51%	2836
	11th to 20th	Day	15% 8% 2 5% 4 4 4 3 5% 5% 45%	2840
	21st to end	Day	18% 9% 3 7% 4 3 4 3 4 5% 39%	3124
February	1st to 10th	Day	13% 7% 3 7% 4 5% 5% 4 6% 7% 41%	1710
	11th to 20th	Day	20% 7% 2 4 4 3 3 3 5% 5% 43%	1696
	21st to end	Day	19% 6% 3 7% 4 4 4 4 5% 7% 36%	1613
March	1st to 10th	Day	20% 8% 2 6% 4 4 4 3 5% 6% 37%	3435
	11th to 20th	Day	10% 5% 2 4 4 4 4 3 6% 7% 53%	3480
	21st to end	Day	21% 6% 2 6% 5% 4 4 4 4 6% 38%	3815
April	1st to 10th	Day	10% 5% 2 5% 3 3 4 4 6% 7% 51%	2266
	11th to 20th	Day	12% 6% 3 5% 4 4 3 3 5% 7% 49%	2254
	21st to end	Day	16% 6% 2 6% 4 4 4 3 5% 7% 43%	2280
May	1st to 10th	Day	15% 8% 3 8% 5% 5% 5% 4 6% 8% 32%	4037
	11th to 20th	Day	21% 7% 2 6% 4 5% 5% 4 6% 8% 32%	4081
	21st to end	Day	9% 4 2 5% 4 4 4 4 6% 11% 46%	4747
June	1st to 10th	Day	10% 4 2 5% 4 4 5% 5% 7% 10% 44%	2660
	11th to 20th	Day	10% 5% 2 5% 5% 4 5% 4 8% 9% 42%	2660
	21st to end	Day	7% 5% 2 5% 5% 5% 6% 5% 7% 10% 43%	2660
July	1st to 10th	Day	6% 5% 2 6% 5% 5% 5% 5% 9% 12% 41%	4260
	11th to 20th	Day	11% 5% 2 6% 5% 4 5% 5% 9% 12% 37%	4120
	21st to end	Day	11% 7% 3 7% 6% 6% 6% 5% 8% 10% 32%	4466
August	1st to 10th	Day	16% 7% 3 7% 5% 5% 5% 5% 7% 10% 30%	4104
	11th to 20th	Day	9% 5% 2 7% 5% 5% 6% 5% 7% 11% 38%	3893
	21st to end	Day	9% 4 2 5% 3 3 5% 4 6% 11% 49%	4180
September	1st to 10th	Day	12% 6% 2 6% 4 5% 4 4 5% 7% 46%	2280
	11th to 20th	Day	13% 6% 2 5% 4 4 4 3 6% 8% 44%	2245
	21st to end	Day	21% 7% 2 8% 4 3 3 3 5% 7% 38%	2000
October	1st to 10th	Day	16% 6% 2 6% 3 4 3 3 4 6% 48%	1900
	11th to 20th	Day	16% 4 2 4 3 4 2 3 4 5% 53%	1900
	21st to end	Day	13% 5% 2 5% 3 3 3 3 3 6% 54%	2090
November	1st to 10th	Day	13% 5% 1 4 3 3 3 3 4 5% 55%	1887
	11th to 20th	Day	15% 5% 2 5% 4 3 3 2 5% 6% 50%	1723
	21st to end	Day	14% 5% 2 5% 3 3 3 3 5% 6% 51%	1520
December	1st to 10th	Day	17% 6% 2 6% 4 4 5% 3 6% 7% 40%	1520
	11th to 20th	Day	16% 6% 2 4 3 3 4 2 3 5% 52%	1910
	21st to end	Day	18% 7% 2 6% 4 4 4 4 5% 7% 39%	2786
January	1st to 10th	Night	14% 7% 2 5% 4 3 4 3 5% 5% 47%	4109
	11th to 20th	Night	18% 7% 3 5% 3 3 3 3 4 5% 47%	4120
	21st to end	Night	21% 8% 2 5% 3 3 3 3 4 4 43%	4532
February	1st to 10th	Night	14% 7% 2 5% 5% 3 4 4 5% 6% 44%	2470
	11th to 20th	Night	19% 7% 2 5% 4 4 4 3 4 6% 43%	2369
	21st to end	Night	17% 7% 2 5% 4 3 3 3 5% 5% 45%	1837
March	1st to 10th	Night	21% 6% 3 6% 3 4 4 3 5% 6% 39%	3418
	11th to 20th	Night	13% 5% 2 5% 4 3 3 3 5% 7% 51%	3480
	21st to end	Night	15% 6% 2 5% 3 3 3 3 4 5% 48%	3817
April	1st to 10th	Night	13% 7% 3 6% 4 4 4 4 4 6% 47%	1913
	11th to 20th	Night	10% 6% 2 4 4 4 4 3 6% 8% 49%	1875
	21st to end	Night	14% 7% 2 5% 4 4 4 4 6% 6% 45%	1900
May	1st to 10th	Night	17% 7% 3 8% 5% 5% 4 3 5% 8% 35%	2887
	11th to 20th	Night	23% 7% 3 7% 4 4 4 3 5% 6% 34%	2812
	21st to end	Night	10% 5% 2 5% 4 4 5% 4 7% 10% 45%	2804
June	1st to 10th	Night	11% 4 2 6% 4 5% 5% 4 7% 9% 42%	1520
	11th to 20th	Night	9% 6% 3 6% 4 5% 5% 4 7% 11% 40%	1520
	21st to end	Night	8% 6% 1 5% 5% 4 5% 4 7% 11% 44%	1520
July	1st to 10th	Night	6% 5% 2 7% 5% 5% 6% 5% 8% 10% 39%	2695
	11th to 20th	Night	9% 6% 2 7% 6% 5% 7% 5% 8% 11% 35%	2840
	21st to end	Night	11% 8% 3 9% 6% 7% 7% 6% 7% 7% 30%	3087
August	1st to 10th	Night	15% 7% 3 8% 4 5% 5% 5% 7% 10% 31%	2825
	11th to 20th	Night	9% 5% 3 8% 4 5% 6% 5% 7% 10% 37%	2903
	21st to end	Night	8% 5% 2 6% 5% 5% 4 4 6% 8% 45%	3476
September	1st to 10th	Night	13% 6% 2 5% 5% 4 5% 3 5% 8% 44%	1900
	11th to 20th	Night	12% 6% 2 5% 4 5% 5% 4 5% 7% 46%	1931
	21st to end	Night	22% 8% 2 5% 4 4 4 4 5% 5% 38%	2179
October	1st to 10th	Night	16% 6% 3 5% 3 4 4 3 5% 5% 46%	2280
	11th to 20th	Night	15% 5% 1 5% 4 3 3 3 4 7% 49%	2280
	21st to end	Night	12% 4 2 5% 3 4 3 3 4 6% 52%	2508
November	1st to 10th	Night	12% 7% 2 5% 4 3 3 3 5% 5% 51%	2264
	11th to 20th	Night	14% 6% 2 4 3 3 4 3 4 5% 51%	2450
	21st to end	Night	13% 4 2 4 3 3 5% 4 5% 7% 50%	2660
December	1st to 10th	Night	17% 8% 3 5% 4 3 4 3 5% 5% 43%	2660
	11th to 20th	Night	17% 7% 2 4 4 3 3 2 5% 5% 47%	3285
	21st to end	Night	16% 7% 2 5% 4 4 4 4 5% 7% 41%	4852

Transparency (when cloud cover <= 30%)
Color Meanings: Too cloudy to forecast Poor Below Average Average Above average Transparent
Month	Days in Month		Occurrence of each Forecast	Data Points
January	1st to 10th	Day	36% 4 6% 32% 17% 5%	2837
	11th to 20th	Day	40% 5% 7% 20% 22% 6%	2840
	21st to end	Day	47% 4 9% 21% 15% 3	3124
February	1st to 10th	Day	42% 6% 9% 26% 14% 3	1710
	11th to 20th	Day	42% 5% 7% 22% 20% 5%	1705
	21st to end	Day	47% 5% 12% 14% 17% 5%	1613
March	1st to 10th	Day	46% 6% 9% 19% 13% 7%	3435
	11th to 20th	Day	29% 6% 8% 23% 24% 10%	3480
	21st to end	Day	46% 6% 9% 18% 17% 3	3815
April	1st to 10th	Day	31% 6% 12% 22% 20% 9%	2266
	11th to 20th	Day	35% 5% 11% 22% 21% 7%	2254
	21st to end	Day	41% 6% 11% 22% 16% 5%	2280
May	1st to 10th	Day	47% 9% 13% 18% 11% 2	4074
	11th to 20th	Day	47% 8% 12% 21% 11% 1	4085
	21st to end	Day	30% 8% 17% 22% 21% 2	4761
June	1st to 10th	Day	33% 8% 17% 25% 16% 1	2660
	11th to 20th	Day	35% 10% 16% 22% 16% 2	2660
	21st to end	Day	33% 10% 16% 24% 15% 2	2660
July	1st to 10th	Day	32% 10% 24% 17% 11% 5%	4195
	11th to 20th	Day	37% 8% 23% 23% 8% 1	4051
	21st to end	Day	44% 10% 13% 19% 14% 1	4324
August	1st to 10th	Day	46% 8% 17% 21% 7% 1	4091
	11th to 20th	Day	36% 10% 18% 24% 12% 1	3932
	21st to end	Day	29% 7% 17% 28% 17% 2	4180
September	1st to 10th	Day	37% 7% 13% 17% 22% 4	2280
	11th to 20th	Day	38% 7% 8% 24% 19% 4	2245
	21st to end	Day	47% 5% 9% 19% 16% 4	2000
October	1st to 10th	Day	35% 4 8% 18% 29% 5%	3160
	11th to 20th	Day	23% 4 6% 21% 32% 14%	3140
	21st to end	Day	20% 3 10% 29% 26% 12%	3428
November	1st to 10th	Day	32% 4 8% 24% 27% 5%	1887
	11th to 20th	Day	36% 3 9% 21% 22% 8%	1723
	21st to end	Day	34% 5% 8% 23% 25% 5%	1520
December	1st to 10th	Day	42% 5% 11% 23% 15% 4	1520
	11th to 20th	Day	36% 4 7% 29% 17% 7%	1906
	21st to end	Day	43% 6% 10% 26% 14% 2	2786
January	1st to 10th	Night	38% 4 8% 23% 22% 5%	4109
	11th to 20th	Night	40% 4 7% 21% 23% 5%	4120
	21st to end	Night	45% 4 6% 22% 16% 6%	4532
February	1st to 10th	Night	40% 5% 10% 24% 18% 3	2470
	11th to 20th	Night	43% 4 7% 20% 19% 7%	2371
	21st to end	Night	41% 4 8% 22% 18% 7%	1837
March	1st to 10th	Night	45% 5% 9% 22% 16% 3	3418
	11th to 20th	Night	32% 5% 7% 21% 27% 9%	3480
	21st to end	Night	38% 5% 8% 23% 21% 5%	3817
April	1st to 10th	Night	39% 6% 9% 17% 23% 7%	1913
	11th to 20th	Night	33% 5% 12% 22% 22% 6%	1875
	21st to end	Night	38% 6% 12% 23% 16% 6%	1900
May	1st to 10th	Night	46% 8% 14% 19% 11% 2	2915
	11th to 20th	Night	49% 8% 11% 22% 9% 1	2813
	21st to end	Night	31% 10% 16% 26% 15% 2	2811
June	1st to 10th	Night	36% 9% 13% 26% 15% 1	1520
	11th to 20th	Night	35% 10% 17% 21% 15% 2	1520
	21st to end	Night	33% 8% 15% 22% 18% 4	1520
July	1st to 10th	Night	37% 12% 20% 16% 12% 3	2650
	11th to 20th	Night	39% 12% 21% 20% 7% 1	2786
	21st to end	Night	49% 10% 13% 17% 11%	2988
August	1st to 10th	Night	47% 8% 16% 22% 7%	2814
	11th to 20th	Night	38% 9% 18% 24% 11%	2930
	21st to end	Night	35% 8% 12% 30% 14% 2	3476
September	1st to 10th	Night	39% 7% 14% 17% 17% 6%	1900
	11th to 20th	Night	38% 6% 10% 22% 22% 3	1931
	21st to end	Night	48% 6% 10% 18% 15% 3	2179
October	1st to 10th	Night	39% 6% 10% 18% 22% 5%	3800
	11th to 20th	Night	25% 3 8% 21% 31% 11%	3779
	21st to end	Night	21% 3 7% 31% 26% 13%	4120
November	1st to 10th	Night	35% 5% 8% 21% 25% 6%	2264
	11th to 20th	Night	36% 5% 8% 20% 23% 9%	2450
	21st to end	Night	33% 5% 8% 25% 22% 6%	2660
December	1st to 10th	Night	43% 5% 8% 23% 17% 4	2660
	11th to 20th	Night	39% 4 8% 22% 21% 7%	3288
	21st to end	Night	40% 7% 11% 24% 16% 2	4852

Seeing (when cloud cover <= 80%)
Color Meanings: Too cloudy to forecast Bad 1/5 Poor 2/5 Average 3/5 Good 4/5 Excellent 5/5
Month	Days in Month		Occurrence of each Forecast	Data Points
January	1st to 10th	Day	28% 21% 27% 17% 6%	270
	11th to 20th	Day	28% 26% 32% 11% 3	270
	21st to end	Day	28% 17% 39% 12% 3	297
February	1st to 10th	Day	24% 21% 37% 14% 4	270
	11th to 20th	Day	37% 23% 29% 8% 2	303
	21st to end	Day	30% 17% 30% 19% 3	382
March	1st to 10th	Day	22% 22% 31% 20% 6%	460
	11th to 20th	Day	23% 22% 33% 16% 5% 1	460
	21st to end	Day	25% 17% 35% 17% 6% 1	506
April	1st to 10th	Day	23% 21% 29% 18% 7% 1	460
	11th to 20th	Day	21% 13% 34% 20% 9% 4	452
	21st to end	Day	23% 12% 35% 21% 7% 2	460
May	1st to 10th	Day	22% 13% 31% 22% 9% 3	463
	11th to 20th	Day	23% 7% 28% 25% 13% 3	487
	21st to end	Day	18% 4 22% 30% 21% 5%	529
June	1st to 10th	Day	11% 5% 27% 30% 22% 6%	490
	11th to 20th	Day	11% 6% 23% 32% 18% 9%	490
	21st to end	Day	11% 6% 23% 33% 21% 7%	490
July	1st to 10th	Day	10% 4 17% 31% 28% 11%	485
	11th to 20th	Day	6% 2 17% 35% 29% 11%	484
	21st to end	Day	10% 4 21% 31% 24% 10%	532
August	1st to 10th	Day	13% 4 21% 27% 27% 8%	486
	11th to 20th	Day	12% 3 15% 31% 27% 11%	479
	21st to end	Day	10% 3 15% 29% 27% 16%	539
September	1st to 10th	Day	15% 5% 18% 26% 22% 16%	490
	11th to 20th	Day	15% 4 16% 31% 22% 11%	490
	21st to end	Day	28% 8% 20% 27% 12% 5%	490
October	1st to 10th	Day	23% 5% 23% 24% 18% 8%	490
	11th to 20th	Day	17% 12% 21% 28% 20% 3	490
	21st to end	Day	15% 12% 32% 26% 11% 4	539
November	1st to 10th	Day	17% 10% 28% 26% 15% 4	467
	11th to 20th	Day	19% 12% 30% 25% 12% 2	368
	21st to end	Day	21% 15% 28% 25% 8% 3	180
December	1st to 10th	Day	24% 15% 38% 14% 8% 2	180
	11th to 20th	Day	24% 14% 31% 22% 7% 1	180
	21st to end	Day	29% 14% 29% 17% 9% 2	204
January	1st to 10th	Night	20% 18% 35% 23% 3	760
	11th to 20th	Night	22% 17% 31% 27% 4	760
	21st to end	Night	21% 15% 38% 24% 3	836
February	1st to 10th	Night	21% 14% 36% 26% 3	760
	11th to 20th	Night	25% 17% 37% 18% 2	743
	21st to end	Night	24% 16% 35% 23% 3	628
March	1st to 10th	Night	19% 15% 36% 27% 3	760
	11th to 20th	Night	22% 16% 34% 21% 6%	760
	21st to end	Night	18% 14% 39% 24% 5%	836
April	1st to 10th	Night	17% 17% 36% 24% 5%	760
	11th to 20th	Night	13% 14% 37% 28% 8% 1	751
	21st to end	Night	18% 8% 35% 32% 7%	760
May	1st to 10th	Night	18% 8% 32% 33% 8% 1	619
	11th to 20th	Night	18% 6% 24% 36% 15% 1	561
	21st to end	Night	13% 3 18% 40% 24% 2	458
June	1st to 10th	Night	10% 3 19% 46% 22% 1	380
	11th to 20th	Night	11% 3 19% 41% 24% 3	380
	21st to end	Night	8% 2 22% 45% 22% 1	380
July	1st to 10th	Night	12% 3 13% 39% 29% 3	462
	11th to 20th	Night	5% 1 11% 42% 36% 5%	552
	21st to end	Night	8% 3 17% 42% 26% 4	624
August	1st to 10th	Night	11% 2 13% 43% 28% 3	567
	11th to 20th	Night	13% 2 11% 41% 29% 4	630
	21st to end	Night	10% 3 14% 35% 33% 5%	836
September	1st to 10th	Night	15% 3 12% 36% 28% 6%	760
	11th to 20th	Night	14% 4 15% 33% 31% 4	760
	21st to end	Night	24% 5% 18% 34% 19% 1	760
October	1st to 10th	Night	18% 4 19% 33% 21% 4	760
	11th to 20th	Night	18% 8% 27% 29% 18% 1	760
	21st to end	Night	16% 9% 28% 31% 15% 1	836
November	1st to 10th	Night	16% 8% 27% 33% 14% 2	755
	11th to 20th	Night	17% 12% 30% 30% 10% 1	760
	21st to end	Night	14% 13% 31% 32% 9% 1	760
December	1st to 10th	Night	22% 13% 32% 26% 8%	760
	11th to 20th	Night	19% 11% 33% 32% 6%	760
	21st to end	Night	22% 14% 26% 33% 4	836

Page generated at 2024-11-01 22:47:36. Version ac07

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